Block That Changes Other Blocks Around It

So I'm making a mod that remakes old Minecraft features and adds them back to the game and one of them is The Nether Reactor Core. Basically I want to make a block that responds to a certain action by changing all the blocks in a 50x50 radius to other blocks Eg: Stone - Netherrack, Dirt - Soul Soil. If this is possible which I'm not even sure it is in MCreator how would I pull it off? If it isn't does anyone have a different idea for The Nether Reactor Core?